It’s not (just) the directory name. This error message (transport endpoint is not connected) basically never happens for any typical local file systems, like ext4, btrfs, etc., and it’s most commonly encountered when using fuse or a networked file system. What file system do you use on /mnt/data?
No, I can’t unfortunately. Restarting the server fixes this problem and unmounting and remounting the mount point seems like it could also fix this problem. This is all based on what I have read online if anyone else reads this post. You could also downgrade mhddfs to 0.1.38 to fix this issue. And there is a github repo called mhddfs-nosegfault that fixes this issue.
If I replaced the original mhddfs with the custom package (mhddfs-nosegfault) in the /bin directory will the OS use the custom package?